This application claims benefit of Japanese Application Nos. 2000-238987 filed on Aug. 7, 2000, and 2000-238988 filed on Aug. 7, 2000 the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a camera and in particular relates to a camera having a diopter adjustment mechanism whereby the observation diopter of the rangefinder device can be adjusted from outside by moving part of an optical element comprised in the rangefinder device, by manual action by the user.
2. Description of the Related Art
In cameras whereby photography/image pickup is performed, conventionally, various proposals have been made concerning the provision of a rangefinder device comprising a rangefinder optical system formed by an objective optical system, inverting optical system, and eyepiece optical system, whereby a user can ascertain and observe the range of field of view including a desired image to be observed, and these are in general practical use.
An example of such a rangefinder device in a conventional camera is a so-called real image type rangefinder device constructed such that the observed image formed by the objective optical system is converted into an erect real image through the inverting optical system, which is magnified by the eyepiece optical system and can then be observed. Such a xe2x80x9crangefinderxe2x80x9d device is commonly referred to as a xe2x80x9cfinderxe2x80x9d device.
Usually, in a conventional real image type rangefinder device, an observation diopter is set so that the most suitable observation of the rangefinder image is obtained by a typical observer of normal visual acuity i.e. a so-called normal observer.
However, with a rangefinder device in which the observation diopter of the rangefinder device is previously determined in this way to a prescribed value, when the rangefinder image produced by this rangefinder device is observed by an observer whose visual acuity does not match that of the hypothetical observer (i.e. normal observer), that is, a myopic observer or hypermetropic observer etc, a clear rangefinder image cannot be observed due to the mismatch of observation diopter.
Accordingly, the rangefinder devices in conventional cameras etc are provided with a so-called diopter adjustment mechanism whereby the observation diopter of the rangefinder device can be adjusted at will in a prescribed range such as to produce an observation diopter capable of matching the visual acuity of the observer; various such proposals have been made and have been generally put into practice. An example is disclosed in Laid-open Japanese Patent Publication No. H8-110559.
Such diopter adjustment mechanisms are implemented, for example, by providing a mechanism whereby at least one of the optical components such as an optical element like an eyepiece lens constituting part of the eyepiece optical system can be displaced within a prescribed range in a prescribed direction (such as the direction along the optic axis), thereby enabling the observation diopter to be adjusted at will from outside by manual operation of a prescribed operating member.
For example, in a camera equipped with a diopter adjustment mechanism for adjusting the observation diopter of the rangefinder device so as to provide an observation diopter at which observation by the observer is easy, the aforementioned Laid-open Japanese Patent Publication No. H8-110559 discloses the provision of a diopter adjustment mechanism to enable the displacement in the direction along the optic axis i.e. the forwards/rearwards direction with respect to the camera body of part of the eyepiece optical system in a rangefinder optical system, by means of an operating member (operating knob etc) and an end face cam member that rotates integrally therewith, arranged on the side of a camera casing member. By this means, adjustment can be achieved such that an optimum observation diopter is produced for clear observation of the rangefinder image, by operating the operating member from outside.
In such a conventional diopter adjustment mechanism arranged in a camera rangefinder device, there may be provided for example an operating member and an indication such as a prescribed index in order to display the set condition of the observation diopter in response to the set position of the operating member in the vicinity thereof, in order to confirm the condition of the observation diopter corresponding to the position of setting of the operating member.
However, if the camera is operated by a user who is unaccustomed to the operating procedure and an adjustment mechanism requires a complicated operation, the user may not understand which operating member is to be operated in what manner, since the user may not have the knowledge or experience necessary to operate it. In such cases, it is conceivable that incorrect operation may be performed such as that even an emmetropic user may adjust the setting of the observation diopter to that intended for a hypermetropic person or myopic person. Thus, if the observation diopter is not correctly set in accordance with the visual acuity of the user, because of inappropriate operation, convenience and ease of operation when using this device may of course be impaired.
Accordingly, in order to prevent this state of affairs, consideration has been given to explicit indication in what condition the observation diopter is set relative to the set position of the operating member, by relating the observation diopter of the rangefinder image with the set position of this operating member when the operating member has been operated.
However, in a construction such as the means disclosed by the above Laid-open Japanese Patent Publication No. H8-110559 i.e. a construction in which an operating member (operating knob) for moving the rangefinder optical system (eyepiece lens) is mounted on a casing member of the camera and the eyepiece lens constituting the driven member that is driven by this operating member is provided in the camera body, there are the following problems. Specifically, there is the problem that, if dimensional errors produced during manufacture of the various structural members and assembly errors produced during assembly thereof combine, offset may be produced in the observation diopter that should be set in respect of the position of the operating member. It is needed to provide means to maintain the relative relationship in which the observation diopter always gets equal to the prescribed observation diopter when the operating member is arranged in the prescribed position.
It can also happen that the operating member for adjustment of the observation diopter is moved whilst the camera is in use, resulting in setting of the observation diopter to a different value to that set by the user. Some means is therefore necessary whereby, while the operating member for activating the diopter adjustment mechanism is constructed such that it can easily be operated to perform setting, once setting of the observation diopter has been performed, this operating member is not easily displaced from its set position.
The present invention was made in view of the above, an object thereof being to provide by a more straightforward construction a camera having a diopter adjustment mechanism whereby the observation diopter of the rangefinder device can be adjusted from outside by a moving part (driven member) of an optical element comprised in the rangefinder device, by operation of the operating member by the user. That camera is provided with a diopter adjustment mechanism capable of always ensuring a relative positional relationship of the operating member and driven member such that when the operating member is arranged in a prescribed position the observation diopter gets equal to the prescribed observation diopter which should be set.
Also, a further object of the present invention is to provide a camera wherein, when the operating member is arranged in a standard prescribed set position, it is arranged that the operating member cannot be unintentionally displaced, and that the fact that the operating member is in the standard position can easily be identified, thereby contributing to improvement in ease of operation.
A camera according to the present invention comprises a rangefinder device having an optical system constituted by a plurality of optical elements and a diopter adjustment mechanism capable of adjusting the observation diopter of the rangefinder device by operation by the user from the exterior of the camera. Furthermore, it comprises an operating member for actuating the diopter adjustment mechanism and an adjustment mechanism for effecting adjustment such that the observation diopter of the rangefinder device is a predetermined value when the operating member is in a prescribed position.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description referring to the accompanying drawings.